Infants & Young Children Vol. 18, No. 2, pp. 86–103 c 2005 …depts.washington.edu/isei/iyc/fidler_18_2.pdf · 2007-08-16 · LWW/IYC lwwj057-03 March 9, 2005 14:26 Char Count=

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Infants & Young ChildrenVol. 18, No. 2, pp. 86–103c© 2005 Lippincott Williams & Wilkins, Inc.

The Emerging DownSyndrome BehavioralPhenotype in Early ChildhoodImplications for Practice

Deborah J. Fidler, PhD

Previous studies have reported a specific behavioral phenotype, or a distinct profile of behav-ioral outcomes, associated with Down syndrome. Until recently, however, there has been littleattention given to how this behavioral profile emerges and develops over time. It is argued herethat some aspects of the Down syndrome behavioral phenotype are already emerging in infantsand toddlers, including emerging relative strengths in some aspects of visual processing, recep-tive language and nonverbal social functioning, and relative weaknesses in gross motor skills andexpressive language skills. Research on the early developmental trajectory associated with Downsyndrome (and other genetic disorders) is important because it can help researchers and practi-tioners formulate interventions that are time-sensitive, and that prevent or offset potential futurenegative outcomes. This article reviews evidence for the emerging Down syndrome behavioralphenotype in infants, toddlers, and preschoolers. This is followed by a discussion of interventionapproaches that specifically target this developing profile, with a focus on language, preliteracyskills, and personality motivation. Key words: behavioral phenotypes, Down syndrome, earlyintervention

DOWN syndrome is the most common ge-netic (chromosomal) mental retardation

syndrome, occurring in from 1 in 700 to 1in 1000 live births (Hassold & Jacobs, 1984;Stoll, Alembik, Dott, & Roth, 1990). In 95%of cases, Down syndrome is caused by an ex-tra chromosome 21 (trisomy 21). Commonphysical features associated with Down syn-drome are a distinctive craniofacial structureand health-related issues like congenital heartdisease, middle ear disease, and immune and

From the Human Development & Family Studies,Colorado State University, Fort Collins.

The author thanks Susan Hepburn, PhD, and AmyPhilofsky, MA, CCC-SLP, for their ideas and commentson early drafts of this article. The author also thanksSally Rogers, PhD, for her guidance on this project.

Corresponding author: Deborah J. Fidler, PhD, 102 Gif-ford Building, 502 West Lake St, Colorado State Uni-versity, Fort Collins, CO 80523 (e-mail: [email protected]).

endocrine system abnormalities (Pueschel &Pueschel, 1992).

Over the past few decades, research hasbegun to converge on a specific behavioralphenotype, or a distinct profile of behav-ioral outcomes, associated with Down syn-drome as well. According to recent studies,the Down syndrome behavioral phenotype in-cludes relative strengths in some aspects ofvisuospatial processing (Jarrold & Baddeley,1997; Jarrold, Baddeley, & Hewes, 1999; Klein& Mervis, 1999; Wang & Bellugi, 1994), andsocial functioning (Gibbs & Thorpe, 1983;Rodgers, 1987; Wishart & Johnston, 1990),as well as relative deficits in verbal pro-cessing (Byrne, Buckley, MacDonald, & Bird,1995; Hesketh & Chapman, 1998; Jarroldet al., 1999; Laws, 1998) and some aspectsof motor functioning (Chen & Woolley, 1978;Dunst, 1988; Fidler, Hepburn, Mankin, &Rogers, in press; Jobling, 1998; Mon-Williamset al., 2001). Language has been described asa “major area of deficit” in Down syndrome

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Early Development in Down Syndrome 87

(Sigman & Ruskin, 1999), with particu-lar difficulties manifested in expressive lan-guage (Miller & Leddy, 1999). In addition,individuals with Down syndrome have beendescribed as showing a distinct personal-ity motivation profile (Pitcairn & Wishart,1994).

Researchers often acknowledge 2 impor-tant issues when studying behavioral pheno-types (Dykens & Hodapp, 2001). First, theyacknowledge that behavioral phenotypes areprobabilistic. As such, groups with a certainsyndrome are more likely to show one ormore “characteristic”behaviors than other in-dividuals with mental retardation, but notevery child with a specific syndrome nec-essarily shows all etiology-specific behaviors(Dykens, 1995; Hodapp, 1997). Addition-ally, researchers note that some syndromesshare certain behavioral outcomes with othergenetic disorders, so outcomes are oftennot specific to a particular syndrome. Inseveral genetic disorders of mental retarda-tion (eg, fragile X syndrome, Williams syn-drome), for example, many children show hy-peractivity or attention problems (Hodapp,1997).

DEVELOPMENTAL CONSIDERATIONS

Amidst the recent advances in behav-ioral phenotype research (Dykens & Hodapp,2001), researchers have also begun to ar-gue for the importance of understandinghow phenotypes develop and change overtime (Karmiloff-Smith, 1997). Rather thanconsidering outcomes as preserved or dam-aged modules that are wholly intact or im-paired uniformly throughout development,Karmiloff-Smith (1998) argues that “tiny vari-ations in the initial state” can become magni-fied throughout development into domains ofrelative strength and weakness. Early develop-ment may be a crucial window of opportu-nity for intervention, as these “tiny variations”have not yet snowballed into impairments inwhole domains of processing. Studies to datethat have taken a developmental approach to

behavioral phenotypes have shown that ar-eas of purported relative strength at one stageof development (middle childhood or adoles-cence) may not have been relatively strongerat other stages of development (early child-hood; Paterson, Brown, Gsoedl, Johnson, &Karmiloff-Smith, 1999). There may be crucialwindows of opportunity in early developmentto target areas that pose potential problems tochildren with Down syndrome before they be-come pronounced areas of weakness. Thus,understanding how the Down syndrome be-havioral phenotype emerges over the first fewyears of early development may help shape ef-fective, time-sensitive intervention for youngchildren with Down syndrome and theirfamilies.

EARLY EMERGENCE OF THE DOWNSYNDROME BEHAVIORAL PHENOTYPE

Compared to other genetic disorders, earlydevelopment in Down syndrome has receiveda good deal of research attention. Develop-ment in infancy and toddlerhood has rarelybeen studied in other genetic disorders suchas Prader-Willi syndrome, Williams syndrome,or Smith-Magenis syndrome. Even in thosefew existing studies on early developmentin other syndromes, the focus is primarilyon issues such as early feeding in infancy(Morris, Demsey, Leonad, Dilts, & Blackburn,1988), rather than on the development of var-ious aspects of cognitive-linguistic or social-emotional functioning.

The wealth of research on early develop-ment in Down syndrome may be attributedto the higher incidence of Down syndromethan that of other genetic syndromes, as wellas technological advances enabling early iden-tification of Down syndrome. Since the late1960s, it has been possible to screen preg-nant women for Down syndrome via amnio-centesis and karyotyping of fetal cells. In addi-tion, in most neonatal units, diagnostic testingis standard procedure for any newbornsshowing the cardiovascular, craniofacial, orother physical features associated with Down


88 INFANTS & YOUNG CHILDREN/APRIL–JUNE 2005

syndrome. This stands in contrast with the de-lay of diagnosis often seen in other geneticdisorders, for example, Williams syndrome(Huang, Sadler, O’Riordan, & Robin, 2002;Morris et al., 1988).

Thus, early identification has facilitated thedescription of early social-emotional function-ing, cognitive-linguistic development, person-ality motivation, and motoric functioning inyoung children with Down syndrome over thefirst few years of life. This research can beseen as a description of the early initial statesof an emerging behavioral phenotype and canhelp shed light on how the specific outcomesin genetic disorders change and become morepronounced throughout development.

The following section discusses research ondifferent domains of development, includingcognitive, linguistic, motor, social-emotional,and motivational functioning. For each do-main of development, functioning in olderchildren, adolescents, and young adults withDown syndrome is discussed. Then, researchon related findings in early development—orwhat could be considered the “developmen-tal precursors” to these later outcomes—isdiscussed.

Cognitive functioning

Children, adolescents, and young adults

Research on the cognitive phenotype inadolescents and adults with Down syndromehas most recently focused on deficits in ver-bal working memory, and on how they re-late to poor expressive language and learn-ing outcomes (Byrne et al., 1995; Hesketh &Chapman, 1998; Jarrold, Baddeley, & Phillips,2002; Laws, 1998). In addition, studies havefound relative strengths in visuospatial pro-cessing in this population, and many individ-uals with Down syndrome have a profile ofstronger visuospatial than verbal processingskills (Jarrold et al., 1999; Klein & Mervis,1999; Wang & Bellugi, 1994). Amidst theserelative strengths in visuospatial processing,there is preliminary evidence that some as-pects of visuospatial processing are stronger

than others in older children and young adultswith Down syndrome (Fidler, 2005). In par-ticular, visual memory visual-motor integra-tion, and especially visual imitation seem tobe areas of relative strength within visuospa-tial processing, whereas spatial memory andvisuoconstructive tasks seem to be areas ofrelative weakness (Fidler, 2005).

Early developmental precursors

Can evidence of this cognitive profile al-ready be found in early development? Laterdeficits in auditory processing could be linkedto atypical auditory brain-stem responses ininfants with Down syndrome in the first yearof life (Folsom, Widen, & Wilson, 1983). Inaddition, the high incidence of congenitalanomalies of the ear in this population—otitis media, for example—has been linked todeficits in auditory processing in early devel-opment as well (Downs & Balkany, 1988). Buta distinction must be made between auditoryperception and short-term/working mem-ory for auditorally presented information, asJarrold et al. (2002) have identified a short-term memory deficit for auditorally presentedverbal information in older individuals thatcannot be attributed to sensory deficits. Itmay be that poor vocal imitation in infantswith Down syndrome is linked to later deficitsin verbal working memory in this popula-tion, but this connection should be exploredfurther (Mahoney, Glover, & Finger, 1981;Rondal, 1980). It may also be important toconsider that precursors to deficits in verbalworking memory and related cognitive skillsmay not be present in early childhood andmay emerge later in development.

Evidence of strengths in visual processingin early development in Down syndrome canbe found in studies of infant visual recognitionmemory, where infants with Down syndromeshow similar event-related brain potentialmorphology, visual attention, and visual fix-ation to typically developing infants (Karrer,Karrer, Bloom, Chaney, & Davis, 1998; Karrer,Wojtascek, & Davis, 1995). Infants with Downsyndrome have even shown evidence of faster



information processing than have typical in-fants on some components of visual mem-ory (Karrer et al., 1995). In line with findingsof strong visual imitation skills in older chil-dren, there are also reports of early visual (notvocal) imitative competence in infants withDown syndrome, similar to the performanceof typically developing infants (Heiman &Ulstadius, 1999).

However, not all areas of visuospatial func-tioning are relatively strong in young childrenwith Down syndrome, a finding that couldbe associated with ocular abnormalities com-monly found in this population (Niva, 1988;Woodhouse et al., 1996). Gunn, Berry, andAndrews (1982) report that 6-month-old in-fants with Down syndrome show delays in vi-sual exploration in play situations with theirmothers (Gunn et al., 1982). Other reports de-scribe impaired visual attention performanceon a habituation task in infants with Downsyndrome (Miranda & Fantz, 1973), and de-lays in various aspects of eye contact in infantswith Down syndrome, including the func-tional use of eye contact to explore the en-vironment in a parent-child interactive set-ting (Berger & Cunningham, 1983). Theseearly development findings also suggest thatin both infancy and later development, mix-tures of strengths and weaknesses can befound within this area of functioning.

Language, speech, and communication


Many children with Down syndrome havesevere language delays (Sigman & Ruskin,1999). Part of the Down syndrome lan-guage phenotype includes pronounced im-pairments in expressive language relative toreceptive language, including large deficitsin vocabulary size relative to mental age(Chapman, 1999; Fabretti, Pizzuto, Vicari, &Voterra, 1997). In terms of receptive lan-guage, whereas receptive vocabulary is MAappropriate in later childhood and adoles-cence, comprehension of syntax lags behind(Abbeduto et al., 2003; Chapman, Schwartz,

& Kay-Raining Bird, 1991). Individuals withDown syndrome also show particular deficitsin the development of grammar, and manyadults with Down syndrome do not progressbeyond the early stages of morphologicaland syntactic development (Fowler, 1990). Interms of speech, Miller and Leddy (1999) re-port that articulation and speech intelligibil-ity is a major challenge for many individualswith Down syndrome as well. However, de-spite deficits in language and speech, older in-dividuals with Down syndrome show relativestrengths in nonverbal communication (Miller& Leddy, 1999).


A similar profile of deficits in languageand speech development, but strengths incommunicative competence, can already befound in early development of children withDown syndrome. In terms of speech and ex-pressive language, atypical vocalizing is al-ready evident in infants with Down syndromefrom 2 to 12 months, who produce atypicalprelinguistic phrases compared to those pro-duced by typically developing infants (Lynch,Oller, Steffens, & Buder, 1995). In the first 6months of life, infants with Down syndromealso produce more non–speech-like soundsthan speech-like sounds, which may nega-tively impact the later development of nor-mal vocal behavior (Legerstee, Bowman, &Fels, 1992). Additionally, delays in age of on-set of canonical babbling have been found ininfants with Down syndrome (Lynch, Oller,Steffens, Levine, et al., 1995). In contrastwith the relatively strong visual imitative com-petence in young children with Down syn-drome, as mentioned earlier, vocal imitationseems to be greatly impaired (Mahoney et al.,1981; Rondal, 1980). Decreased vocal imi-tation in Down syndrome has been shownto be associated with lower expressive andreceptive language skills (Mahoney et al.,1981).

Nevertheless, other aspects of prelinguis-tic vocal development seem to be on par



with typically developing infants, includingthe amount of vocalization produced, de-velopmental timetable of vocalizations, andcharacteristics of consonants and vowels pro-duced during babbling (Oller & Seibert, 1988;Smith & Oller, 1981; Smith & Stoel-Gammon,1996; Steffens, Oller, Lynch, & Urbano,1992).

One of the most important studies of earlyspeech and language functioning in Downsyndrome has demonstrated that the major-ity (64%) of children with Down syndromeaged 0 to 5 years fit a profile of receptive lan-guage that is mental age appropriate while ex-pressive language lags behind (Miller, 1999).In addition, this study found that over time,the number of children who fit this profileincreased to 72%, suggesting that some chil-dren may be “growing into”this profile as theydevelop. Miller (1999) reported that thereseemed to be 2 distinct groups of young chil-dren with Down syndrome—one group thatshowed impairment from the onset of firstwords and a second group that acquired vo-cabulary but showed expressive language lagswhen language learning advanced to more dif-ficult skills, such as the combining of wordsinto phrases.

In terms of early communicative compe-tence, some areas seem to be intact whereasothers are impaired. Young children withDown syndrome show MA-appropriate levelsof nonverbal joint attention (Fidler, Philofsky,Hepburn, & Rogers, in press; Mundy, Kasari,Sigman, & Ruskin, 1995; Mundy, Sigman,Kasari, & Yirmiya, 1988; Wetherby, Yonclas,& Bryan, 1989). In addition, despite deficits inexpressive language development, the earlyuse of gestures in children with Down syn-drome seems to be intact. One study founda “gesture advantage” in young children withDown syndrome compared with controlsmatched for word comprehension (Caselliet al., 1998). Another study found that despitea smaller repertoire of gestures, no differ-ences could be found for overall usage ofgestures between young children withDown syndrome and a comparison groupof language-age–matched children (Iverson,

Longobardi, & Caselli, 2003). Yet, even in thecontext of these communicative strengths,other aspects of early communicative com-petence seem to be impaired. In particular,young children with Down syndrome showdeficits in nonverbal requesting behaviors(Mundy et al., 1988, 1995; Fidler et al., inpress; Wetherby et al., 1989).

Social-emotional functioning


Although deficits in speech, language, andcommunication are common, many older in-dividuals with Down syndrome nonethelessshow relative strengths in social function-ing. For example, individuals with Down syn-drome may show relative competence informing relationships with others. Freemanand Kasari (2002) found that the majority ofchildren with Down syndrome in their sam-ple showed relationships with peers that metcriteria for true friendships—reciprocal nom-ination in the friendship dyad, convergencebetween parental and child nomination, andat least 6-month stability of friendship in thatdyad. Children with Down syndrome havealso been shown to be more empathic thanother children with developmental disabili-ties, showing more prosocial responses in asimulated distress situation (Kasari, Freeman,& Bass, 2003). Children with Down syn-drome may also “overuse” their social skillsto compensate for other weaker domains offunctioning (Freeman & Kasari, 2002). In animpossible task study, for example, young chil-dren with Down syndrome showed looks tothe experimenter and more “party pieces,”or charming off-task behaviors that engagedthe experimenter socially (Pitcairn & Wishart,1994).

Children with Down syndrome may alsosend more positive emotional signals thanmay other children with mental retardation.In one study, 5- to 12-year-olds with Down syn-drome smiled more frequently than childrenwith other mental retardation syndromes, al-though this finding of increased smile fre-quency changed as individuals with Down



syndrome approached adulthood (Fidler &Barrett, in press).


Some aspects of this socioemotional profileare already present in infancy. Visual imitativecompetence in infancy has been describedas evidence of “an innate social competence”(Heiman & Ulstadius, 1999). In terms of earlylooking behavior, Crown, Feldstein, Jasnow,and Beebe (1992) found that infants withDown syndrome look longer at their moth-ers than typically developing infants even at 4months of age, a behavior that may promoteconnections with others. These findings areechoed in a study by Gunn et al. (1982), whofound that 6- and 9-month-olds with Downsyndrome spent nearly half of their interac-tion time looking toward their mother, and byKasari, Freeman, Mundy, and Sigman (1995),who found increased looking behavior at par-ents during an ambiguous situation. However,in the context of increased looking behav-ior, Kasari et al. (1995) and Walden, Kneips,and Baxter (1991) found decreased socialreferencing.

Other evidence of social competence ininfancy can be found in increased melodicsounds, vocalic sounds, and emotional soundsin 4-month-old infants with Down syndromewhen interacting with people rather thanwith objects (Legerstee, Bowman, & Fels,1992). Evidence of continued social com-petence seems to continue throughout tod-dlerhood and pre-school–aged children withDown syndrome. At 17.5 months, infantswith Down syndrome show responses to ma-ternal requests that are similar to those re-sponses made by typically developing infants(Bressanutti, Sachs, & Mahoney, 1992). In amodified strange situation, 24-month-oldswith Down syndrome show distress whentheir mothers are absent, with increased cry-ing and noncrying distress and increasedlooks at the door—behavior described as sim-ilar to that observed in typically develop-ing children (Berry, Gunn, & Andrews, 1980;see also Vaughn et al., 1994). Toddlers andpreschoolers with Down syndrome also dis-

play relative strengths in certain types ofnonverbal social interaction including moreplay acts, turn taking, invitations, and objectshows compared to typically developing chil-dren (Mundy et al., 1988; Sigman & Ruskin,1999).

One aspect of social-emotional function-ing in Down syndrome that may be of par-ticular interest is the ability to communicatepositive affect through frequent emotion dis-plays such as smiles. Initial studies of emo-tion communication in infants with Downsyndrome reported muted emotion displaysand less emotional lability than typically devel-oping infants (Berger & Cunningham, 1986;Buckhalt, Rutherford, & Goldberg, 1978;Cicchetti & Sroufe, 1978; Emde & Brown,1978; Rothbart & Hanson, 1983). Later stud-ies, however, that were conducted with moreobjective coding systems (ie, MAX and FACS),suggested that although there may be morefrequent low-intensity smiling in young chil-dren with Down syndrome, this may be in ad-dition to frequent high-intensity smiling, suchthat there may actually be more smiling andincreased emotional lability in young childrenwith Down syndrome than in typically de-veloping children (Kasari, Mundy, Yirmiya, &Sigman, 1990; Kneips, Walder, & Baxter,1994). These findings are in line with thefinding of increased smiling behavior in olderchildren and preadolescents with Down syn-drome (Fidler & Barrett, in press).

Motor functioning

Overview

Another aspect of the Down syndrome be-havioral phenotype described in older individ-uals involves difficulties with motor skills andmotor planning (Jobling, 1998; Mon-Williamset al., 2001). Jobling (1998) reported that 10-to 16-year-old children with Down syndromehave specific motor impairments, includingdifficulty with precise movements of limbs(eg, stepping over a stick while on a bal-ance beam) and fingers (eg, pivoting thumband index finger) as well as gross motor taskssuch as sit-ups and push-ups. Similar relative



weaknesses have been demonstrated in mo-tor planning or praxis (Mon-Williams et al.,2001). However, in other domains such asrunning speed and agility and visual-motorcontrol, Jobling (1998) reports that child per-formance in Down syndrome can be at CAlevels.

Developmental precursors

Most infants and toddlers with Down syn-drome show extreme motor delays relativeto CA-matched typically developing infants,moving through stages of early motor de-velopment more slowly and exhibiting morewithin-group variability than typically devel-oping infants (Chen & Woolley, 1978; Dunst,1988). Abnormal movement patterns, hypoto-nia, and hyperflexibility are common in thispopulation (Harris & Shea, 1991). In addition,delays in the emergence and termination ofreflexes are prevalent in early motor develop-ment in this population (Block, 1991; Harris& Shea, 1991). These atypical outcomes seemto become more evident toward the end ofthe first year of life (Dunst, 1988; Henderson,1985).

Dmitriev (2001) describes 4 different typesof infants with Down syndrome on the basisof muscle tone and motor functioning. Type 1(15%–25%) babies have good muscle tone andshow milestones like head control, bearingweight on feet with support and lifting thetorso on extended arms by 4 months. Types2 and 3 (50%–60%) babies show a discrep-ancy between upper and lower body mo-tor functioning. Type 2 infants have strongupper back, neck, shoulders, and arms, butare unable to bear weight on their legs asother infants are able to do, whereas Type 3infants have strong legs and lower torso,but weaker upper torso, neck, head, shoul-ders, and arms. Finally Type 4 babies (15%–25%) are weak all over, with flaccid arms andlegs, and often have accompanying cardio-vascular challenges. These groupings suggestthat although there is variability within Downsyndrome motor functioning in infancy, themajority of infants do face serious motor chal-lenges that warrant intervention.

In terms of motor planning, infants withDown syndrome show more deviation fromstraight lines and changes in plane of motionduring reaching behavior than typically de-veloping infants, evidence of a deficit in theorganization of reaching movement (Cadoret& Beuter, 1994). Fidler et al. (in press) ex-plored whether motor delays in Down syn-drome include deficits in motor planning, andwhether motor planning is related to adaptivefunctioning in this population. Toddlers withDown syndrome in this study performed sig-nificantly worse on a battery of motor plan-ning tasks, including reaching into a jar tograsp a nerf ball, and stringing beads, a find-ing specific to Down syndrome and not at-tributable to disability status in general. Fur-thermore, partial correlations demonstrateda strong association between overall adap-tive motor functioning and motor planningperformance in both disability groups evenwhen age was partialled out. Similar asso-ciations were found between motor plan-ning and daily living skills, suggesting thatmotor planning deficits in Down syndromemay also be associated with day-to-day adap-tation, and not only motor-related adaptiveskills.

Personality motivation

Overview

Individuals with Down syndrome have fre-quently been described as having charm-ing personalities, often in accordance with apositive Down syndrome personality stereo-type (Gibbs & Thorpe, 1983; Rodgers, 1987;Wishart & Johnston, 1990). Older childrenand young adults with Down syndrome are de-scribed as of primarily positive mood and pre-dictable in their behavior, but less active andpersistent and more distractible than otherchildren as well (Gunn & Cuskelly, 1991).In one study, over 50% of 11-year-old chil-dren with Down syndrome were described as“affectionate,” “lovable,” “nice,” and “gettingon well with other people,”and many childrenwere also described as “cheerful,”“generous,”and “fun”(Carr, 1995).



Alongside these positive perceptions, manyindividuals with Down syndrome are alsodescribed as showing inconsistency in mo-tivational orientation. Many children withDown syndrome also show lower levels oftask persistence and higher levels of off-taskbehavior tasks, interfering with task com-pletion (Landry & Chapieski, 1990; Pitcairn& Wishart, 1994; Ruskin, Kasari, Mundy, &Sigman, 1994; Vlachou & Ferrell, 2000). Theseindividuals are sometimes described as stub-born or strong willed, traits that may con-tribute to inconsistent performance on tasksdue to task refusal (Carr, 1995; Gibson, 1978).

Developmental precursors

Several studies report no significant tem-perament differences between infants withDown syndrome and typical infants in earlyinfancy, at 2 months (Ohr & Fagen, 1994) andlater at 12 to 36 months (Vaughn, Contreras, &Seifer, 1994). Other studies, however, reportthat young children with Down syndrome(M = 30 months) are rated as of more positivemood, more rhythmic, and less intense thanCA-matched children (Gunn & Berry, 1985).These findings echo the findings of increasedpredictability, increased positive mood, anddecreased persistence in older children withDown syndrome. However, nearly one thirdof children with Down syndrome in Gunn andBerry’s (1985) study showed signs of difficulttemperament as well, a possible precursor tostubbornness and other behavior problems.

The developmental precursors of task per-sistence findings may also be identifiablein early development. Young children withDown syndrome often show inconsistent per-formance on assessment measures from time-point to timepoint (Morss, 1983; Wishart &Duffy, 1990). Wishart and Duffy (1990) foundthat children with Down syndrome aged 6months to 4 years show highly inconsistentperformances on the same testing batteryacross sessions 2 weeks apart. The authorssuggested that this inconsistency is the resultof motivational issues, often the result of re-fusal to engage fully in tasks at either time-point (Wishart & Duffy, 1990).

Morss (1983) has similarly reported thatinfants with Down syndrome repeat theirsuccesses on tasks less often than mental,age-matched, typically developing children.Hasan and Messer (1997) found that childrenwith Down syndrome in their sample showedmore stability in performance on executivefunction/object permanence and other cog-nitive tasks although 20% of their sampledid show some regressions. Researchers sug-gest that these regressions often result from achild’s unwillingness to engage in a task, sug-gesting that motivation may be an importantfactor for assessing development in Down syn-drome (Pitcairn & Wishart, 1994; Wishart &Duffy, 1990).

According to Wishart (1993), “[F]rom avery early age, it would appear that the Downsyndrome children are avoiding opportunitiesfor learning new skills, making poor use ofskills that are acquired, and failing to consoli-date skills into their repertoires.” Along theselines, increased level of help elicitation hasalso been found in Down syndrome and mayrelate to persistence issues as well. In the mo-tor planning study described above (Fidler,Hepburn, Mankin, & Rogers, in press), it wasalso found that toddlers with Down syndromeelicited significantly more help on the ob-ject retrieval task than did children in bothcomparison groups, a finding also reported inother studies (Freeman & Kasari, 2002).

Overall profile of early developmentin Down syndrome

In addition to exploring the early devel-opment of various aspects of functioningin Down syndrome, it may also be impor-tant to explore “cross-domain relations,” orhow different domains of functioning developtogether (Hodapp, 1996). Are pronounceddissociations between areas of strength andweakness already observable in early child-hood? In a recent study, Fidler et al. (in press)described the performances of young chil-dren with Down syndrome on measures ofvisual processing, expressive language, recep-tive language, fine and gross motor function-ing, and social functioning on the Mullen



Scale of Early Learning (Mullen, 1995). Theirperformance was compared to the perfor-mance of a group of children with other devel-opmental disabilities and a group of typicallydeveloping children, with all groups equatedon mental age.

Toddlers with Down syndrome in this studydid show relative strengths in the areas of vi-sual processing and receptive language, andrelative weaknesses in gross motor skills andexpressive language, although it is importantto note that these dissociations were small inmagnitude. In terms of parent-reported skillsin adaptive behavior in real-life situations, thechildren with Down syndrome in this studyshowed relative strengths in socialization andrelative weaknesses in communication andmotor skills. This is evidence that phenotypicpattern of strengths and weaknesses associ-ated with Down syndrome is emerging bythe age of 2, with between-group differencesin sociability, and within-group patterns ofrelative strengths and weaknesses that fore-shadow the phenotype described in studies ofolder persons.

It is notable that the dissociations observedwithin the individuals with Down syndromewere significant, but also relatively small atthese early developmental ages. Even in thesignificant difference between expressive andreceptive language, differences averaged only2.5 months in age-equivalent scores. In otherstudies with older children with Down syn-drome, dissociations between domains offunctioning can be much larger. This does notminimize the rapid changes that take placeover several months in early development. Butthe relatively small dissociation is also notablefor intervention purposes—because areas ofstrength and weakness are less pronouncedearly on, it may be possible to reduce thesedissociations and set areas of potential weak-ness on more optimal pathways.

With this understanding of the early emer-gence of the Down syndrome behavioral phe-notype in infants and toddlers, it may be possi-ble to shape intervention that is sensitive notonly to the current functioning level of thechild but also to the developmental trajectory

associated with their genetic disorder. Ratherthan waiting for a dissociated pattern to takeits full form, interventions can focus on pre-venting these dissociations from taking place.

USING BEHAVIORAL PHENOTYPERESEARCH TO INFORM EARLYINTERVENTION IN DOWN SYNDROME

One of the most interesting questions thatarise from behavioral phenotype researchconcerns the influences of child transactionalhistory on the developing behavioral phe-notype. Is it possible to help children withDown syndrome follow more optimal devel-opment pathways? This section will exploreapproaches that show promise—interventionapproaches that are informed by behavioralphenotype research.

Amidst the many proposed theoreticalapproaches to intervention in Down syn-drome, researchers have introduced yet an-other approach—focusing on behavioral phe-notype research (Hodapp & DesJardin, 2003;Hodapp & Fidler, 1999). This approach arguesthat education and intervention may be moreeffective when it specifically targets the de-velopmental trajectory associated with a par-ticular syndrome. The behavioral phenotypeapproach is housed within the larger move-ment of developmental interventions, whereprogramming decisions are informed by de-velopmental theory (see Spiker, 1990, for areview).

The importance of time sensitivity and earlyimplementation in intervention has also beendemonstrated in this population. In one study,a 2-month delay of treatment for young chil-dren with Down syndrome was associatedwith lower gross motor, fine motor, language,and social outcomes at 18 months (Sanz &Menendez, 1995). In another study, infantswho received language intervention begin-ning as newborns showed more optimal out-comes than did infants who started the inter-vention at 90 and 180 days of age (Sanz &Balana, 2002).

Yet, the efficacy of intervention in Downsyndrome and other groups remains in



question (for reviews, see Gibson & Fields,1984; Gunn & Berry, 1989; Guralnick, 1996;Nilholm, 1996). The implementation of justany intervention is not sufficient for im-proving developmental outcomes (Crombie &Gunn, 1998; Gibson & Fields, 1984). In ad-dition, some interventions that have becomepopular at different points have been ineffec-tive. For example, popular high-dosage mul-tivitamin and mineral supplements that havebeen administered to infants and childrenwith Down syndrome aged 7.5–63 monthshave been shown to be associated with de-creased, rather than increased, developmen-tal progress, according to one study (Bidder,Gray, Newcombe, & Evans, 1989). These high-dosage multivitamins and supplements mayalso be associated with unpleasant side effectsas well. Nevertheless, parents report improve-ments in child appearance and skin tone withthese products, and some parents report thatthey would recommend the vitamin therapyto other parents of children with Down syn-drome (Bidder et al., 1989).

With the increased prevalence of alterna-tive and unconventional therapies aimed atparents of children with disabilities and theirchildren, there is a strong need for inter-ventions that are rooted in good science.At this point in time, interventions that areinformed by behavioral phenotype researchhave not been tested in the literature. Test-ing the tenability of such an approach willneed to involve scientific rigor and the highstandards found in other types of treatmenttrials (Kasari, 2002). Yet, there is promise inthis approach that it is rooted in good sci-ence, and it is in line with recommendationsthat educational programs target “the specificlearning abilities and disabilities of Down syn-drome individuals” (Nadel, 1996). A prelimi-nary sampling of intervention ideas that areinformed by behavioral phenotype research isdescribed in the following section.

Cognitive-linguistic functioningand intervention

If individuals with Down syndrome doshow an advantage for processing visuospa-

tial, rather than verbal information, mightthis information be used to improve develop-mental outcomes in this population? Severalsuggestions have been made to this effect(Byrne et al., 1995; Chapman, 1995; Gibson,1991). Pueschel, Gallagher, Zartler, andPezzullo (1987) noted that “[t]eaching strate-gies should capitalize on Down syndromechildren’s strengths and should focus onvisual-vocal and visual-motor processingmodalities in remediation” (p. 35). They alsonote that “increasing emphasis on auditoryteaching strategies may lead to frustration inthe child and may impede academic process”(p. 35). Indeed, a recent study demonstratesthat children with Down syndrome respondbetter to scaffolding that involves bothspeech and gestures (visual) than to scaffoldsthat involve only speech (Wang, Bernas, &Eberhard, 2001).

Yet amidst the many recommendations foran increased attention on visual processing inDown syndrome, there have been relativelyfew efforts to utilize this processing modeto improve outcomes. According to Nadel(1996), “there has been scant application ofknowledge about the specific learning abili-ties and disabilities of Down syndrome indi-viduals to the development of these programs”(p. 22).

One exception is the movement to em-phasize early reading in young children withDown syndrome (Buckley, Bird, & Byrne,1996; Oelwein, 1995; Oelwein, Fewell, &Pruess, 1985). Buckley and colleagues sug-gest that it is possible to improve languageand memory functioning by establishing earlysight vocabularies in children with Down syn-drome (Buckley et al., 1996). They argue that

[T]he benefits of learning to read go beyond sim-ply acquiring a functionally useful level of read-ing and writing skill . . . reading can develop speechand language skills, auditory perceptional skills andworking memory function; all areas where childrenwith Down syndrome usually display difficulties.(p. 269)

Early sight vocabularies for children withDown syndrome capitalize on their strengths



in visual memory to recognize and identifywords, making logographic reading possibleat young ages. Buckley et al. (1996) cite casestudies of children with Down syndrome whoare 2 and 3 years old and who have greatlybenefited from the establishment of sight vo-cabularies, findings that have been echoedby parents as well (eg, Carter, 1985; Duffen,1976).

Another group advocating the use of earlysight vocabularies is team at the Universityof Washington Model Preschool Program forChildren with Down Syndrome and OtherDevelopmental Delays (Oelwein, 1988). Ac-knowledging that most preschoolers do notreceive formal reading instruction, Oelweindescribed the decision to teach reading topreschoolers with Down syndrome as onethat provided a solution for children who“had very well-developed visual discrimina-tion skills, but virtually no spoken language.”This approach advocates scheduling 5 to 7minutes of reading instruction during short,individualized sessions 2 to 4 days per week.Data collected on children in this programsuggest that children with Down syndromecan develop sight vocabularies at all levels ofIQ, and that reading level is highly related toreceptive language scores—not IQ. These sug-gestions are well justified and target areas ofdistinct strength in the developing Down syn-drome behavioral phenotype.

However, more evidence is needed to sub-stantiate the claim that reading can impactother areas of development (Kemp, 1996;Lorenz, Sloper, & Cunningham, 1985).

Language outcomes

More direct routes to improving languageoutcomes can also be informed by behav-ioral phenotype research in Down syndromeas well. Miller (1999) argues that it is un-necessary for—and may be detrimental to—children with Down syndrome to wait foralmost inevitable deficits in expressive lan-guage to become apparent and then docu-mented. He argues that linguistic phenotyperesearch in Down syndrome demonstrates theinevitability of expressive language deficits,

and as such, a diagnosis of Down syndromeshould automatically make a child eligible forspeech and language intervention services.Miller (1999) also argues that language inter-vention should focus on targeting and pre-venting expressive language impairments inDown syndrome before they become pro-nounced. Continuous reinforcement for vo-calizations in infants between 2 and 8 monthshas been shown to increase vocalization rates(Poulson, 1988), a promising technique to en-courage precursors to expressive language.

In addition, some have suggested thatlanguage intervention should promote oralmotor functioning in Down syndrome, whilefacilitating communication regardless ofmodality (verbal or nonverbal; Miller, 1999).As such, it may be beneficial to target oraldyspraxia early in speech therapy. Parentscan be taught to use techniques such asback-chaining, prompt-fading, and socialpraise as a reward for effort. Other rec-ommendations have been made to targetthe difficult transition in Down syndromefrom babbling to meaningful speech. Forexample, Stoel-Gammon (2001) recommendsthat adults offer phonetically contingent re-sponses to prelinguistic vocalizations duringinfancy. These responses can help an infantunderstand and start to produce meaningfulutterances. Stoel-Gammon (2001) also sug-gests the use of sound games to facilitate theawareness of sound-meaning relationships ininfants and toddlers with Down syndrome.It may also be helpful to provide nonverbalmeans of communicating in the first years oflife (eg, gestures, picture exchange, sign lan-guage), in addition to building language skills,as a way of minimizing frustration. These andother recommendations specifically targetthe developing linguistic phenotype in Downsyndrome and may be more effective becausethey keep an eye toward Down syndromelanguage outcomes in general.

Motivation orientation, socialfunctioning, and intervention

In planning early interventions, caregivers,educators, and therapists must be aware of



the propensity of children with Down syn-drome to avoid challenging tasks via socialinitiation. The development of cognitive, lan-guage, and motor skills relies upon frequentpractice with supports. Avoidance of thesetasks will lead to a broader gap in skills overtime and thus significantly inhibit the emer-gence of adaptive skills.

Help elicitation observed in some studies ofchildren with Down syndrome (Fidler et al., inpress) can be interpreted in several ways. Onone hand, children may be using their abilityto relate to others in ways that help them com-plete tasks more successfully. This may bodewell for individuals who might otherwise notbe able to perform certain daily living skillstasks. On the other hand, most new tasks aredifficult for children at various points of de-velopment, and part of the growth processinvolves challenging oneself to develop skillsin order to overcome obstacles. If individualswith Down syndrome are eliciting help thisearly in development, they may be missing outon important challenging early experiencesthat may promote their growth.

To address the motivational issues in Downsyndrome early development, errorless learn-ing techniques may be important ways to pre-vent task abandonment in Down syndrome(Fidler, in press; Oelwein, 1995). To maximizetask persistence during interventions, practi-tioners and parents may opt for alternate ac-tivities by skill domain (ie, social, expressivelanguage, receptive language, motor), begin-ning and ending with domains of strength (eg,social, receptive language). Intervention ap-proaches can also more readily target areasof deficit by imbedding them in tasks that in-volve areas of strength. For example, to in-crease practice of motor foundation skills, itmay be useful to imbed motor tasks in playand other social contexts.

Dmitriev (2001) recommends an operantconditioning-grounded approach in Downsyndrome that involves rewarding desired be-haviors. He suggests that

actions that result in success or the attainment ofa desired goal—the fun of playing with a new rat-

tle, the feeling of accomplishment and a mother’spraise when a toddler successfully pulls on a pair ofsocks . . . quickly teach the child which behaviorsguarantee success. (p. 68)

An operant conditioning approach may beparticularly helpful for children with Downsyndrome, who can be prone to inconsis-tent performance due to motivational issues(Wishart & Duffy, 1990). A steady flow of pos-itive motivational feedback may serve to con-tinue to motivate children as they proceedthrough a challenging task, especially giventhe social orientation of many children withDown syndrome.

In addition, children with Down syndromeshould be encouraged to use their social skillsin adaptive and appropriate ways. Lloverasand Fornells (1998), for example, recommendsymbolic play group approaches that facili-tate “the construction of relational competen-cies which are needed for . . . social integra-tion and . . . global satisfactory development”(p. 89).

Motor skills and intervention

Recent findings suggest that variousapproaches to early motor intervention—approaches that focus on developmentalfunctioning and approaches that focus onfunctional skills—may have little effecton improving developmental outcomes inDown syndrome and other disability groups(Mahoney, Robinson, & Fewell, 2001). How-ever, these findings may not be generalizableto all intervention studies, particularly be-cause parents were not included in theintervention approaches studied (see discus-sion below).

Building a stronger motor foundation in-volves participation in purposeful, relevantactivities that incorporate specific compo-nents of motor foundation. For example, toimprove and maintain appropriate postureand position, a child may work on theseskills while sitting at a table engaging in atask. The skill development component of theDenver Model intervention involves targetinginitiation actions, imitation of others, hand



development, coordination, and dexterity.This may be especially helpful for young chil-dren with Down syndrome who may havedifficulty with initiation due to hypotoniaand a less persistent temperament, but whoshow strengths in visual imitation due to so-cial and other factors. In this model, skillsare taught using shaping and other prompt-ing techniques, with each skill broken downand chaining procedures are used in multistepsequences (Osaki, Roger, & Hall, 2000). Thisrecommendation is echoed by others for chil-dren with Down syndrome (Dmitriev, 2001).Finally, the compensatory strategies compo-nent of the model includes adaptations to thetask that allow for independence rather thana dependence on prompting and help elicita-tion throughout the task.

General recommendations

Other more general recommendations mayalso be effective in Down syndrome early in-tervention. For example, interventions thatare informed by an understanding of theemerging phenotype in Down syndrome mayenable practitioners to focus on areas ofstrength as a “way in” for interventions thattarget potential areas of weakness. While in-tervention is typically drawn to the relativeweaknesses in an individual’s developmentalphenotype (Hodapp & Zigler, 1990), it mayalso be interesting to consider the emergingphenotype as a reflection of strengths, a com-pensatory pattern constructed from areas ofgreatest competency that promotes adapta-tion and access to preferred people and activ-ities. Working from this framework, interven-tion may choose to target strengths as stronglyas weaknesses, in helping people build a lifethat highlights their talents and interests. Forexample, children with Down syndrome maybe encouraged early on to pursue tasks that in-volve potential future strengths like visual pro-cessing and visual-motor coordination, as wellas their relative strengths in social function-ing and forming social relationships. Further-more, promotion of strengths in targeted waysmay facilitate the bootstrapping of weakerskills.

In addition to focusing on the specific childprofile, a focus on family ecology and theparent-child may be crucial for successful in-tervention in Down syndrome and other dis-ability groups (Spiker, 1990). Bronfenbrenner(1974) was among the first to argue that earlyintervention is most effective if the family is anactive agent in implementation. Early motorintervention that includes parental involve-ment has been shown to have a positive ef-fect on early development in Down syndrome(Torres & Buceta, 1998), while interventionstudies that do not involve parents have beenshown to be less effective (Mahoney et al.,2001; see Spiker, 1990, for a review). Chil-dren may also show better outcomes whenparents are trained directly by practitioners,as studies show that parents who are traineddirectly by clinicians fare better than thosegiven written instructions (Sanz, 1988, 1996).Thus, the larger movement toward targetingintervention to both the child and the contextin which the child develops may play an im-portant role in improving developmental out-comes in Down syndrome as well.

SUMMARY

As a part of a larger movement towardstudying the behavioral phenotypes associ-ated with different genetic disorders, thisarticle explored the early developmental pre-cursors to the Down syndrome behavioralphenotype. There is evidence that cognitive,linguistic, social, emotional, motivational, andmotoric aspects of the Down syndrome be-havioral phenotype are already emerging inthe earliest years of life. In addition, cross-domain relations observed in older individualswith Down syndrome also seem to be emerg-ing already in toddlers, although findings areless pronounced at this early stage than theyare in older children and adults.

In light of this new understanding of devel-opment in genetic syndromes, it may now bepossible to target domains of development,such as expressive language, before they be-come areas of pronounced weakness. These



areas can be targeted via time-sensitive in-terventions that are informed by phenotyperesearch on older individuals with the syn-drome. It may also be possible to use areasof relative strength as a “way in” to thoseareas of weakness, to prevent or offset fu-ture delays, as suggested by early reading ap-proaches that seek to impact language and

memory outcomes. The behavioral pheno-type approach remains unsupported by evi-dence at this point in time and warrants rig-orous scientific testing to verify its utility. Butthis approach is grounded in good science andmay prove to be the next shift in how servicesare delivered to young children with Downsyndrome and other genetic disorders.

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